1. NAME AND TITLE

PHOEL-2: A Monte Carlo Calculation of Initial Energy of Photoelectrons and Compton Electrons Produced by Photons in Water.

PHOEL was packaged in 1978 and replaced by PHOEL-2 in 1979.

2. CONTRIBUTOR

Oak Ridge National Laboratory, Oak Ridge, Tennessee.

3. CODING LANGUAGE AND COMPUTER

Fortran IV; IBM 360/370.

4. NATURE OF PROBLEM SOLVED

PHOEL was designed specifically to provide a source term for a Monte Carlo electron energy degradation and transport code for liquid water being used to study the relative biological effectiveness (RBE) of low-LET radiations at low doses.

PHOEL-2 generates the energies of photoelectrons and Compton electrons in water irradiated by photons having an arbitrary energy spectrum. Options exist for allowing at most only a single Compton scattering, for following photons through successive Compton scattering events until a photoelectron is produced, and for suppressing the photoelectric effect. An Auger electron is assumed to be produced following the ejection of a K-shell photoelectron from oxygen.

5. METHOD OF SOLUTION

PHOEL, using Monte Carlo techniques, assumed an infinite, homogeneous water phantom in which the photon spectrum is uniform throughout. Pair production was neglected, but this did not represent a significant omission for photons with energies below about 10 MeV. The code applied to an infinite, homogeneous water phantom irradiated uniformly with photons of a specified energy spectrum.

PHOEL-2 differs from PHOEL by (1) employing a more realistic handling of the photoelectric cross section as a function of energy, (2) compiling electron spectra instead of storing the energies of every electron produced, (3) eliminating some former input restrictions, and (4) using a different random number generator. PHOEL-2 also does not treat pair production and this should be included for water at photon energies above about 2 MeV.

6. RESTRICTIONS OR LIMITATIONS

None noted.

7. TYPICAL RUNNING TIME

The sample problem ran in 6 seconds on the IBM 360/91.

8. COMPUTER HARDWARE REQUIREMENTS

An IBM 360/370 computer is required.

9. COMPUTER SOFTWARE REQUIREMENTS

A Fortran IV compiler is required.

10. REFERENCE

J. E. Turner, R. N. Hamm, H. A. Wright, J. T. Modolo, and G.M.A.A. Sordi, "User's Manual for PHOEL-2, a Monte Carlo Computer Code for Calculating Energies of Photoelectrons and Compton Electrons in Water," ORNL/TM-6954 (August 1979).

11. CONTENTS OF CODE PACKAGE

Included are the referenced document and one (1.2MB) DOS diskette which contains the source code and sample problem input and output.

12. DATE OF ABSTRACT

March 1982; reviewed February 1983.